Look right, I can remember retro g*mers making jokes about the Game Gear being 2big and 2heavy back in the day, probably in the 2000s. Classic Game Room watchers remember. Same for the Lynx. The Wii U's tea tray controller was derided for being beeeeg. I can also recall people saying that the PS Vita was kinda large back when it came out, which tbf it is pushing the definition of "pocketable" for the boys and takes up a lot of purse space.
It sort of felt like reality broke down in 2017. The first thing I did when the Switch was announced was make a joke about putting a Game Gear in your pocket, but suddenly nobody else gave a damn that the Switch is like ten inches long. Most dildos are not that long.... 
I get that it's a hybrid, but suddenly the dynamic shifted from "if it can't fit my dude pockets it's no good!" to "aw yeah bruh just get a hardcase and throw it in a backpack!" I do support backpack gang, but you almost may as well get a laptop at that point.
Handheld size has become progressively more comical over the years though, with my favourite example being the Steam Deck which is actually considerably longer than a Wii U Gamepad at an XL 13" 
Tell ya what, I couldn't fit that!!
I'm not really against the existence of larger handhelds on its own, I have long fingers and a DS Lite or PS Vita will give me handcramps sometimes. But it's like a weirder version of when all phones became "phablets" and impossible to use with one hand, suddenly all handhelds are as big as the Wii U pad. (Switch Lite excluded, though it's still larger than a Vita) It also seems like the PS Vita and 3DS primed everyone to accept hilariously short battery life? The PSP 3000/Go and DS Lite/DSi could get anywhere from 8 to 20 hours depending on your settings, that was awesome. The 3DS and Vita won't hold out for more than three hours under duress, though. Most modern portable PCs have worse battery than that, even...
I guess I'm just wondering wha happun??? I know there's a large contingent of people who never take handhelds outside the house anyway (based) and just use them on the couch, but I don't think the Deck would be much more pleasant to handle in an armchair or whatever. That's one thicc-ass boi.
people started to demand console game experiences on handheld for the most part.
comoanies decided they wanted to close the gap more, to avoid the situation square enix had with DQ11 (where they basically designed the game side by side with the PS4 version)
handhelds with it got both bigger, and required active cooling, which is part of the reason it got bigger.
I lol/lmao at this assertion because for all the size-queening, the Steam Deck has long since fallen behind intensive games. I do sympathise with wanting the same games on the go and portable, though.
more or less depended on what you wanted to play. For example, Elden Ring being playable was quite huge. BG3 outside of the hiccups in chapter 3 is playable. those kind of experiences basically would have never happened on older devices on game launch.
I don't inherently disagree with the portable PC thing, but lol @ one of the games you cite becoming unplayable partway through. I just feel like these devices are huge without much in exchange...
Anything smaller than a laptop running photorealistic graphics is an affront against God. Laptops are questionable at best and lightweight ones are prone to melting.